class Singleton(type):
	def __init__(cls, name, bases, dict):
		super(Singleton, cls).__init__(name, bases, dict)
		cls.instance = None  
def __call__(cls, *args, **kw): 
	if cls.instance is None:  
		cls.instance = super(Singleton, cls).__call__(*args, **kw) 
	return cls.instance 

class MyClass(object): 
	__metaclass__ = Singleton 

print MyClass() 
print MyClass()